Here are a few different concoctions which go by the name "Tequila Mockingbird":

• 1 1/2 oz tequila
  3/4 oz green creme de menthe
  juice of 1 limes

  (this one appears to be the most common)

• 1/2 cup unsweetened apple cider
  2 oz. tequila
  2 oz. black currant-flavored liqueur (Cassis)
  2 tsp. fresh lime juice

• 2 oz. tequila
  1 oz. limoncello
  1 oz. fresh squeezed lemon juice
  2 dashes Angostura bitters

• 1 1/2 ounces Tequila
  1/2 ounce Triple Sec
  1/2 ounce Blue Curaçao
  2 ounces Orange Juice
  1 ounce Cranberry Juice

• 1 Jalapeño pepper slice
  2 oz Patrón Silver Tequila
  1.5 oz Watermelon-Basil Purée*
  .75 oz Fresh lime juice
  .75 oz Agave syrup (one part agave nectar, one part water)